public void CombineLevelTests()
{
Assert.That( LogFilter.Combine( LogLevelFilter.Error, LogLevelFilter.Fatal ), Is.EqualTo( LogLevelFilter.Error ) );
Assert.That( LogFilter.Combine( LogLevelFilter.None, LogLevelFilter.Fatal ), Is.EqualTo( LogLevelFilter.Fatal ) );
Assert.That( LogFilter.Combine( LogLevelFilter.Error, LogLevelFilter.None ), Is.EqualTo( LogLevelFilter.Error ) );
Assert.That( LogFilter.Combine( LogLevelFilter.None, LogLevelFilter.None ), Is.EqualTo( LogLevelFilter.None ) );
Assert.That( LogFilter.Combine( LogLevelFilter.Info, LogLevelFilter.Error ), Is.EqualTo( LogLevelFilter.Info ) );
}